1. Field of the Invention
This invention relates generally to coverings for architectural openings, and more specifically to a roll-up shade having a cellular structure.
2. Description of the Relevant Art
Window shades composed of multiple layers of fabric arranged to create pockets of still air in their structure are commonly described as cellular shades. Cellular shades are desirable for their ability to not only help insulate an opening, such as a window, but also their pleasing aesthetic appearance.
Some cellular type shades have been of the accordion variety, wherein the cells are collapsed onto one another as a foot rail is raised to create a compact stack. This type of cellular shade typically requires lift cords that are threaded through the interior of the cells.
Conversely, typical roller shades do not utilize lift cords but rather, retraction is accomplished by simply rolling the shade material onto a roller. Fabrication of a roller shade is relatively inexpensive typically comprising cutting the shade material to size, attaching a roller and foot rail to the material and attaching the roller to a head rail. Roller shades are typically fabricated using flat covering materials that comprise one or more plies of fabric.
Several roll-up cellular shades have been devised that combine cellular coverings with the convenience and lower cost of the roll-up shade. One type of roll-up cellular covering is described by Thomas P. Hopper in U.S. Pat. Nos. 4,194,550, and 4,039,019. The roll-up shade coverings described in the Hopper patents comprise two essentially flat sheets that are separated by and held apart by a variety of devices that collapse as the coverings are rolled up. The Hopper shades are designed to maximize the insulating capabilities of the coverings, but because of the flat front and back sheets, the shades tend to lack the aesthetic appeal of more traditional cellular shades. U.S. Pat. No. 5,547,006 is an illustration of a shade which is arguably more aesthetically pleasing than the Hopper shades, resembling a conventional roman shade.